Updating reference values for placental weights in Northern Alberta

Objective The purpose of this study was to establish normal parameters for placental weights and fetal/placental weight ratios. Study design Placentas (2402) from uncomplicated singleton deliveries at the Royal Alexandra Hospital (Edmonton, Alberta) were collected from 1997 to 1998 and weighed after fixation. The nonparametric Mann-Whitney test was applied. Results New reference values were developed for fixed placental weights. Placentas at the 90th percentile were 50 to 100 g heavier than previously reported. Fetal/placental weight ratios at term were similar to published values. Conclusion The new placental weight reference values from our institution represent a recent and local population. New values may partly reflect parallel increases in term birth weights.